Where is the muffler in relationship to the cab? I've posted my setup before, so I apologize for boring everybody again. Mine has the same headers you have, a 3" y-pipe that goes directly into a 24" glasspack, then immediately into a si/so 3" Cherry Bomb Extreme, then immediately into a short 45* dump out of it. I cut the dump arm a little so that it couldn't be seen from the side of the truck. None of the exhaust is visible unless you're under the truck. The glasspack sits under the main part of the cab on the passenger side and the CB muffler is positioned underneath the rear seat and the dump opening is just behind the cab. I have absolutely none of the "drone" any more that you are suffering from, but the sound is awesome. The glasspack acts as a resonator, so not only has it removed the terrible drone, but it also has eliminated the popping and cackling sounds that the CB made before I installed the glasspack. I am hoping to get a camcorder in the near future so I can finally post a clip so everyone can hear what I'm talking about. I will see if I can get some pictures of the exhaust setup today and post them to show you how it's set up. It isn't necessarily the best looking but performs very well. For my truck, I wanted to hear the exhaust, but not see any of the system. That's exactly what I've come up with.

 

they sell these little cones in summit and jegs that play a resonator role, im not sure how well they do it but it might work and you dont have to do your entire exhaust